With the continuous improvement of people's living standard, foam pump has been widely used in daily cosmetic, medicines and other fields, therefore, scientists and technicians keep making new technological improvements for it. For example, Chinese patent no. 200620109913.8 “foam pump”, describes a joint, a reticulated foam meshwork mounted in the liquid inlet pipe of the joint, a screw thread whose upper part is equipped in the joint and engaged with the joint, a body whose upper opening fixed with said thread and a glass ball equipped at the liquid inlet of the body. The body includes a hollow upper pole in the thread with a shaped section, and the upper opening is located in the liquid outlet pipe of the joint and is engaged with it. The lower opening is equipped with a fastener, and includes a hollow lower pole in the thread and the valve body. The upper opening is located in the upper pole and is engaged with it and the lower opening is located in the liquid inlet pipe of the valve body. The pump further includes a spring enclosing the lower pole, and a cylinder piston in the thread and the valve body. The upper opening is equipped in the fastener of the upper pole, while the outer wall of the lower opening contacts and engages with the inner wall of the valve. The pump includes an auxiliary pole in the valve body and the lower pole, which is equipped at the lower opening of the lower pole and can be used for opening or closing the lower opening of the lower pole. The liquid piston is mounted outside the auxiliary pole. Problematically, air admission is realized through the interval cooperation of the upper pole and the lower pole. Therefore, this structure has the defect that if the interval is too large, no one-way valve function can be achieved and if the interval is too small, it is possible to be blocked, leading to poor air admission effect. The compression spring is directly supported between the valve body and the lower pole, making the foam pump too high and incontinent for installation and operation. The foaming structure of such reference is too simple and the foaming effect is not ideal, while the piston structure is too complicated and inconvenient for manufacture and operation. The above indicates that further improvements for this kind of foam valve are required.